The development of mass spectrometric methods for the determination of the primary structure of proteins will be continued and applied to new proteins. The sensitivity of the reductive GCMS method for peptide sequencing will be improved by carrying out the derivatization in the gas phase. Fast-atom bombardment and tandem mass spectrometry will be used to determine peptide sequences. Laser induced fragmentation will be investigated for this purpose. These methodologies will be used to determine the structure of a series of thioredoxins, ubiquitous enzymes present in all organisms from bacteria to man; of a viral coat protein and other proteins. Specific enzymatic and chemical peptide bond cleavage methods will be explored for their specific utility in these studies.